1. Field of the Invention
The present invention relates generally to manufacturing processes and in particular to a method and apparatus for discrete event simulation. Still more particularly, the present invention relates to a computer implemented method, apparatus, and computer usable program code for discrete event simulation of manufacturing and assembly processes.
2. Description of the Related Art
Complex projects such as the manufacturing of large commercial or tactical aircraft require the scheduling and coordination of a plurality of resources. The resources to be coordinated may include materials, component parts, personnel, machinery and factory floor space, in addition to other resources. Scheduling and coordination is particularly important in complex projects since factors such as the overall cost of the project, the time required for completion of the project, and the risk of failure must be accurately estimated. In addition, other variables of importance, such as the overall efficiency of the project, need to be accurately estimated. For example, a determination as to whether one or more resources will be under utilized or even idle for a significant amount of time are variables to be accurately determined.
In currently used scheduling analysis methods, the scheduling process generally begins with task data used to describe the tasks to be performed. This task data, for example, defines task dependencies and estimated task durations. Task dependencies generally express relationships between various tasks, so that the various tasks may be properly ordered. For example, in the construction of large commercial aircraft, a material such as an aluminum sheet material must be procured before fuselage panels may be fabricated. The task data is processed to arrange the various tasks into an ordered set of tasks for the process.
Manufacturing processes are typically dependent upon and constrained by the resources required to execute these processes along with the inherent variabilities which may exist. These dependencies and variabilities are often analyzed in advance of initiating the actual manufacturing process. This type of analysis is typically performed by creating a computer model of the process. This computer model is used to perform a simulation of the manufacturing process. A simulation involves initiating the behavior of some system by a means of an analogous model, situation, or apparatus to gain information. In other words, a simulation is a technique of building a model of a real or proposed system so that the behavior of this system may be studied under specific conditions. One benefit provided by a simulation is an ability to model the behavior of a system as time progresses.
Discrete event simulation is one way to build models to observe time-based or dynamic behaviors of a system. More specifically, discrete event simulation is a technique in which the simulation is advanced from event time to event time rather than using a continuously advancing time clock as in continuous simulations. With discrete event simulation, only points in time at which the states of the model changes are represented. In other words, a discrete event simulation models a series of events in a process. By applying appropriate parameters and running a model using discrete event simulation, the effect of factors, such as availability of limited resources and variability in task duration, may be identified.
Although currently used discrete event simulation methods and scheduling techniques are useful in creating and modeling a process prior to implementing process, the current techniques often do not take into account enough factors needed to model a process, such as a manufacturing process.
Therefore, it would be advantageous to have an improved method and apparatus for creating and performing discrete event simulations.